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At least 289 records · Page 16Linked to original sources
PubMed2003

Habitat-specific demography: evidence for source-sink population structure in a mammal, the pika.

Theory suggests that populations may persist in sink habitats that cannot support replacement-level birth rates. Although it is commonly believed that organisms that can actively select habitat should rarely occur in sinks, the frequency of use of sinks in free-ranging species is not well-documented. We found that a population of American pikas ( Ochotona princeps, Lagomorpha) inhabiting distinct alpine habitats (meadow and snowbed) in Wyoming, USA, had habitat-specific demographic rates that produced a source-sink population structure. Population size increased in both habitats in summer and declined in both habitats in winter, with populations in snowbeds increasing more during summer and decreasing more over winter. Birth rates were consistently higher in meadows and populations in meadows had a consistently higher finite rate of increase (lambda, from life tables) than did those in snowbeds, for which lambda was far below that needed for replacement. Patterns of immigration, population structure, and temporal variation in population size were as expected if meadows were functional sources and snowbeds functional sinks. Patterns of snowmelt differed between habitats, predicted the critical difference in birth rates between habitats, and are a likely primary cause of the differences in habitat-specific birth rates that we observed. This study provides a clear example of source-sink population structure for a mammal.

Animals↗
PubMed1985

The demography of maternal mortality--seven Swedish parishes in the 19th century.

Complications of childbirth is a leading death cause for women of reproductive ages in the developing countries today. The unique Swedish population statistics from the 19th century permit comparable historical studies. In seven Swedish parishes 170 maternal deaths were observed - 595 per 100,000 live births. Eclampsia, obstructed labor and hemorrhage were responsible for 92 deaths, and puerperal sepsis for only 15 deaths. Indirect obstetrical deaths, like pneumonia, tuberculosis, dysentery and heart diseases, accounted for 30.8% (41/133) of the specified death causes. With a time limit of 1 year instead of 42 days following delivery, maternal mortality was increased by 17%. Out of 14 married women 1 died from childbirth. Maternal deaths accounted for 40-50% of all deaths in the central ages of reproduction, leaving the motherless children with a highly increased death risk. Of the live born, 3% survived 5 years after the mothers' death. Of children aged 1-5 only 13% survived 5 years after the mothers death.

Demography↗
PubMed1988

Demography of handedness in two samples of randomly selected adults (N = 2083).

Handedness was examined in relation to sex, race, age, education, occupation, marital status, and religious preferences for two random samples of adults drawn from an urban population. There were statistically significant differences on each variable for the total of 2083 respondents as well as for many subgroups based on combinations of sex, race, and age. The results are compared to previous findings.

Adolescent↗
PubMed1984

A national task analysis of infection control practitioners, 1982. Part One: methodology and demography.

A task analysis survey was conducted in 1982 by the Certification Board of Infection Control ( CBIC ) to determine the tasks performed by ICPs and the knowledge and abilities needed to perform these tasks. Data were obtained from 473 (78.8%) respondents to a nationwide mail survey of 600 ICPs . The respondents represent a randomized, stratified sample of ICPs in various types of U.S. acute care hospitals ranging in size from fewer than 50 beds to more than 500 beds. The results of the survey were used, in part, to develop the Infection Control Certification Examination, offered for the first time on November 19, 1983. According to the survey results, the modal or typical ICP is a white woman between the ages of 31 and 50 years using the title of infection control nurse. She has been employed full time for 2 to 10 years in infection control practice in a Joint Commission on Accreditation of Hospitals (JCAH)--accredited community acute care hospital having 301 to 500 beds. She is working at the supervisory level, is on the nursing department payroll, votes as a member of the hospital's infection control committee, and received her last degree or diploma more than 15 years ago.

Adult↗
PubMed1996

The demography of menopause.

Menopause marks a time of dramatic hormonal and often social change for women. Both risk factors and health needs are likely to change as women pass through menopause. This paper examines the demographic characteristics of the world population of menopausal and post-menopausal women, and also examines the implication of menopause for mortality risks. The numbers of women involved are large. Using age 50 as a proxy for menopause, about 25 million women pass through menopause each year, and we estimate that in 1990 there were 467 million post-menopausal women in the world, with an average age of about 60 years. By 2030, the world population of menopausal and postmenopausal women is projected to increase to 1.2 billion, with 47 million new entrants each year. The mortality implications of menopause are also substantial. Ratios of female to male mortality risks from all causes and from all major cause groups except neoplasms decline to low levels around menopause or shortly thereafter, and then rise again to near unity. This pattern is taken as evidence that the female reproductive period is broadly protective of health, but that this protection disappears after menopause. The main protective effect is through reduced risk of cardiovascular disease mortality, partially offset by increased risks of cancer mortality, particularly of the breast and endometrium.

Adult↗
PubMedDate not supplied

The Gompertz equation as a predictive tool in demography.

The Gompertz demographic model describes rates of aging and age-independent mortality with the parameters alpha and A, respectively. Estimates of these parameters have traditionally been based on the assumption that mortality rates are constant over short to moderate time periods. This assumption is questionable even for very large samples assayed over short time intervals. In this article, we compare several methods for estimating the Gompertz parameters, including some that do not assume constant mortality rates. A maximum likelihood method that does not assume constant mortality rates is shown to be best, based on the bias and variance of the Gompertz parameter estimates. Moreover, we show how the Gompertz equation can then be used to predict mean longevity and the time of the nth percentile of mortality. Methods are also developed that assign confidence intervals to such estimates. In some cases, these statistics may be estimated accurately from only the early deaths of a large cohort, thus providing an opportunity to estimate longevity on long-lived organisms quickly.

Computer Simulation↗
PubMed2025

Estimation of demography and mutation rates from one million haploid genomes.

As genetic sequencing costs have plummeted, datasets with sizes previously unthinkable have begun to appear. Such datasets present opportunities to learn about evolutionary history, particularly via rare alleles that record the very recent past. However, beyond the computational challenges inherent in the analysis of many large-scale datasets, large population-genetic datasets present theoretical problems. In particular, the majority of population-genetic tools require the assumption that each mutant allele in the sample is the result of a single mutation (the "infinite-sites" assumption), which is violated in large samples. Here, we present DR EVIL, a method for estimating mutation rates and recent demographic history from very large samples. DR EVIL avoids the infinite-sites assumption by using a diffusion approximation to a branching-process model with recurrent mutation. This approach results in tractable likelihoods that are accurate for rare alleles. We show that DR EVIL performs well in simulations and apply it to rare-variant data from one million haploid samples. We identify mutation-rate heterogeneity even after accounting for trinucleotide context and methylation status. We also predict that at modern sample sizes, the alleles at most polymorphic sites with high mutation rates represent the descendants of multiple mutation events.

Haploidy↗
PubMed2006

Prevalence and demography of transsexualism in Belgium.

AIM: The Belgian medical world has acknowledged the diagnosis of transsexualism and accepted Sex Reassignment Surgery (SRS) as one of the steps in the treatment of choice since 1985. This prevalence and demographic study analyses data on all Belgian individuals who have undergone SRS since that year. METHODS: All (188) plastic surgeons as well as all gender teams (Antwerp, Bruges, Ghent, and Liège) in Belgium were sent demographic questionnaires to be completed for each of their transsexual patients. RESULTS: The results show an overall prevalence of 1:12,900 for male-to-female and 1:33,800 for female-to-male transsexuals in Belgium. In Wallonia (the French-speaking region of Belgium) the prevalence is significantly lower than in Flanders (the Dutch-speaking region) and in Brussels (the bilingual capital region). In the total Belgian population the male/female sex ratio is 2.43:1, again with a substantial difference between Wallonia on the one hand and Flanders on the other. DISCUSSION AND CONCLUSION: While in Flanders and in Brussels the prevalence is comparable to that in other Western European countries, in Wallonia it is markedly lower. Transsexualism in Wallonia appears to be socially less acceptable: persons suffering from gender dysphoria in that part of Belgium encounter more problems accessing gender clinics and receiving treatment.

Adolescent↗
PubMed2003

Interactions between ecology, demography, capture stress, and profiles of corticosterone and glucose in a free-living population of Australian freshwater crocodiles.

In this study we examined three aspects pertaining to adrenocortical responsiveness in free-ranging Australian freshwater crocodiles (Crocodylus johnstoni). First, we examined the ability of freshwater crocodiles to produce corticosterone in response to a typical capture-stress protocol. A second objective addressed the relationship between capture stress, plasma glucose and corticosterone. Next we examined if variation in basal and capture-stress-induced levels of plasma corticosterone was linked to ecological or demographic factors for individuals in this free-ranging population. Blood samples obtained on three field trips were taken from a cross-sectional sample of the population. Crocodiles were bled once during four time categories at 0, 0.5, 6, and 10h post-capture. Plasma corticosterone increased significantly with time post-capture. Plasma glucose also significantly increased with duration of capture-stress and exhibited a positive and significant relationship with plasma corticosterone. Significant variation in basal or stress induced levels of corticosterone in crocodiles was not associated with any ecological or demographic factors including sex, age class or the year of capture that the crocodiles were sampled from. However, three immature males had basal levels of plasma corticosterone greater than 2 standard deviations above the mean. While crocodiles exhibited a pronounced adrenocortical and hyperglycaemic response to capture stress, limited variation in adrenocortical responsiveness due to ecological and demographic factors was not evident. This feature could arise in part because this population was sampled during a period of environmental benigness.

Adrenal Cortex↗